The general procedure for the synthesis of 4-(1,3-thiazol-2-yl)benzaldehyde from 2-bromothiazole (0.9 mL, 10 mmol) and 4-formylbenzeneboronic acid (1.65 g, 11 mmol) was as follows:(1) Under argon protection, a 2-bromothiazole, 4-formylbenzeneboronic acid, sodium carbonate (2.65 g, 25 mmol), toluene (150 mL), ethanol (30 mL) and water (30 mL) mixture was stirred at room temperature for 30 minutes. (2) Tetrakis(triphenylphosphine)palladium(0) (0.58 mg, 0.5 mmol) was added to the reaction system and the reaction was heated under reflux conditions for 15 hours. (3) After completion of the reaction, the reaction mixture was cooled, poured into water and extracted with ethyl acetate. (4) The organic phases were combined, washed sequentially with water and brine, and then dried with anhydrous magnesium sulfate. (5) The organic phase was concentrated under reduced pressure, and the obtained residue was purified by silica gel column chromatography, and finally recrystallized with a mixed solvent of ethyl acetate/hexane to obtain the target product 4-(2-thiazolyl)benzaldehyde (1.4 g, 74% yield). The product was analyzed by elemental analysis (C10H7NOS) and showed the following: melting point 91.5-92.5 °C; calculated values: C, 63.47; H, 3.73; N, 7.40; measured values: C, 63.67; H, 3.60; N, 7.31. 1H-NMR (CDCl3) δ: 7.46 (1H, d, J = 3.2 Hz), 7.95-7.99 ( 3H, m).
